Tuesday, May 10th 2022, 8:47 pm - A sudden and intense warm-up would likely bring catastrophic flooding to parts of the province. It's a low probability event that would have high impacts.
A province that is no stranger to natural disasters finds itself with an intensifying flood risk over the coming weeks.
As has been the trend the past couple of months, below seasonal temperatures dominate the narrative once again this week –- and perhaps they'll be record-breakingly cold.
The coast will see high temperatures hover in the single digits, and that's unheard of for parts of Vancouver Island and Metro Vancouver for the second week of May. The most recent high below 10°C in May for Vancouver occurred on May 6, 2002, at 8.8°C.
It's a temperature recorded hundreds of times for coastal stations in January, but to see the mercury fail to reach double-digits in May is troublesome; mostly, it's because of what's falling above.
By mid-May, the snowpack is usually on the downward trajectory, adding meltwater into the watershed, known as the spring freshet season. What was running a little behind schedule a couple of weeks ago is now beyond fashionably late, so it's now downright problematic.
Snowpack is a single, although important, variable in the spring flood recipe for the province. A higher snowpack is associated with an increased risk of flooding.
But, what's even more important than the depth of the snowpack? The timing of the snowmelt.
Is it slow and gradual, or rapid? Here's the outlook of snowfall through mid-May.
2021 left major burn scars from ferocious wildfires. Those regions might be more likely to increase flows into the watershed, something we certainly don't need this year.
What's left? Well, it's the most vital variable for the next month or so.
A sudden and intense warm-up would likely bring catastrophic flooding to parts of the province. It's a low probability event that would have high impacts.
The more likely scenario is a gradual warm-up with heavy rainfall associated with several cold low-pressure systems that spiral moisture into the watershed, enhancing runoff. Flooding will still occur, but it'll be more localized in nature. These systems can exacerbate flooding caused by snowmelt-driven flows.
There's no cause for alarm for the next 7-10 days. The onshore, cool pattern will continue adding more strain to the watershed. It's the type of problem that can be ignored only for so long, like dirty laundry or dishes piling up.
Come on, stubborn snowpack – it's time to come down. Just not all at once.
Thumbnail courtesy of Abbotsford Police Department/Twitter.